This invention relates to a child safety seat for use in a vehicle of the type comprising a seat body having a seat back, a harness for a child occupant of the seat, secured to the seat body and including a pair of shoulder straps extending through respective slots in the seat back to a mechanism for adjusting the length of the shoulder straps projecting through said slots, means for varying the height at which the shoulder straps project from the seat back, a respective pad slidably mounted on each shoulder strap and having a cover formed of high friction material on the side thereof facing the child occupant""s body, and a respective tether strap having one end attached to each pad and projecting through the same slot in the seat back as the corresponding shoulder strap for limiting movement of the corresponding chest pad along the shoulder strap to a predetermined limit distance away from the seat back. When such a seat is used with the child occupant facing forwards in the vehicle, the shoulder straps tend to stretch during the peak period of deceleration encountered during an accident, allowing angular movement of the child""s upper torso about the child""s pelvis. This allows forward movement of the child""s head and upper torso to such an extent that there is a risk of the child""s head making contact with a hard surface of the vehicle. This forward movement is reduced by the chest pads which frictionally engage with the child""s clothing and which are secured to the seat back by the tether straps. Since the tether straps are relatively short compared with the shoulder straps, they are subject to a much smaller degree of elongation. The overall effect is to reduce forward movement of the head and upper torso of the child.
When the seat is being used by a relatively small child, the chest pads are both undesirable and unnecessary. They are undesirable because they cause a load to be applied to the child""s chest which is excessive for a young child but acceptable for an older child. They are unnecessary because such a child""s body is lighter and therefore its inertia does not cause the shoulder straps to stretch to the same extent as for an older child and also because the child""s body is smaller so that the same angular movement of the child""s upper torso relative to the lower torso results in a smaller extent of forward movement of the child""s head.
It is an object of the invention to provide a child safety seat of the type described above which is suitable for use by a relatively young child and by an older child.
According to the invention, in a child""s safety seat of the type described above, each tether strap is attached to adjustment means for increasing said limit distance as the height at which the shoulder straps project from the seat back is increased.
In one form of the invention, each tether strap is secured to a connection location on the corresponding shoulder strap behind the seat back and a blocker is secured to each tether strap between the connection location and the slots in the seat back, the blocker being dimensioned to abut against the seat back surrounding the slots so as to restrict the length of tether strap which can be protracted through the corresponding slot in the seat back while allowing continued protraction of the shoulder strap.
The length of the tether straps which can be protracted through their slot is chosen so that the chest pads are correctly positioned on the chest of an older child. When the harness is adjusted for use by a younger child, the chest pads are drawn towards the slots until they abut against the seat back. In this position, they are positioned on the shoulders of a child rather than on the chest and do not impose such a large load on the child""s body.
Preferably, the tether straps are linked to the connection locations on the shoulder straps by elastic so as to allow continued shortening of the shoulder straps after the chest pads have come into abutment with the seat back surrounding the slots.